Electrical impulse counting circuits



Sept. 4, 1945. s. B. INGRAM 2,384,379

ELECTRICAL IMPULSE COUNTING CIRCUIT Filed March 15, 1943 [NIT/ALLY CONDUCTING F/QZ m succssuuva ruaz FROM Tiscsoma l was f' 5 C WW WW mo 70 PRECED/NG SUCCEED/NG TUBE TUE //vv/v TOR s. B. INGRAM A 7'7'ORNEV Patented Sept. 4, 1945 ELECTRICAL IMPULSE COUNTING CIRCUITS Sydney B. Ingram, Falrlawn, N. 1., asrignor to Bell Telephone Laboratories, Incorporated,

New

York, N. Y., a corporation oi New York Application March 13, 1943, Serial N o. 479,139

3 Claims. (01. 250-27) This invention relates to automatic counting of electrical impulses by means 01 thermionic vacuum tubes and more particularly to the interconnection of pairs of vacuum tubes in a chain whereby the first of a plurality of successive impulses of electrical potential, which it is desired to count, causes a first tube of one pair to conduct Iull plate current thereby raising, above cut-off, the grid potential 01 the second tube of the preceding pair thus rendering its mate non-conducting and priming the first tube of the succeeding pair in readiness to conduct upon receipt of the next impulse.

Circuits employing gas-filled discharge devices for counting rapidly recurring electrical impulses are well known in the art as, for example, the Thyratron counting circuits described by C. E. Wynn-Williams in the Proceedings of the Royal Society (British) Series A, volume 132 (1931), page 295 et seq. which counting circuits comprise a chain of three-electrode gas-filled devices which successively fire in response to recurring impulses, but, in general, such counting circuits require, as active elements, ionic devices having a trigger action, that is, devices in which conduction between the anode and cathode is initiated by an increase in potential of a control electrode but which conduction will not be affected when the control potential is decreased or completely removed.

Thermionic vacuum tubes have not in the past been used in counting circuits of the Wynn-Willlams type because they do not possess such trigger action but in the present invention such trigger action is obtained by an elementary circuit employing a pair of vacuum tubes which trigger action is the property of the arrangement of the circuit and not of the tubes per se. Such elementary circuits may be the well-known Eccles-Jordan arrangement, as shown in British Patent 148,582 and also described in the Radio Review (1919) volume 1, page 143 et seq. which circuit has two stable conditions of operation, i. e., when one tube is conducting the drop in its plate circuit resistance causes a negative bias to be applied to the grid of its mate thus maintaining it in a non-conducting condition which may be referred to as the first stable condition but when a potential is applied to this latter tube suflicient to raise its grid potential above its critical or socalled cut-ofi point the other stable condition results, that is, the non-conducting tube now conducts which causes the grid of the first tube, which was originally conducting, to become sufiiciently negative to decrease its plate current which, in turn, decreases the negative potential on the grid of its mate, which action transfers back and Iorth between the two tubes and finally results in minimum conduction in the first or originally conducting tube and maximum conduction in its mate. Such an arrangement oi two vacuum tubes constitutes a trigger circuit in that a conducting tube of the pair can be rendered non-conducting by applying such an independent potential to the grid of its non-conducting mate as to cause it to conduct thereby changing the circuit from one stable condition to the other.

A feature oi the invention resides in so connecting a plurality of vacuum tube trigger circuits that they will operate similarly to counting chains of the prior art employing gas-filled devices which in themselves possess trigger properties.

The invention will be understood from the following description when read in connection with the accompanying drawing, Fig. 1 of which shows a basic trigger circuit of the Eccles-Jordan type, and Fig. 2 shows the combination of a plurality of these circuits in a counting chain.

In describing the arrangement of the present invention, a brief description will first be given 01 the operation of the trigger circuit of Fig. l, as more fully described in the before-mentioned British Patent 148,582. This figure (1) shows two vacuum tubes T1 and T2 connected in such a manner that the arrangement has two stable conditions of operation, i. e., when one tube (ior example T2) is conducting, the potential drop in its plate circuit resistance Ri causes a negative bias to be applied to the grid of its mate (Ti) thus holding that tube non-conducting. When a positive voltage from the outside is applied to the grid of T1, which is sufilcient to raise its potential above cut-off, the arrangement assumes the other stable condition, i. e., T1 conducting and T2 non-conducting, due to the potential drop in resistance R1, which condition persists after the disappearance of the outside potential stimulus, applied to the grid of T1, until a later positive potential from the outside is applied to the grid of Ta whereupon the foregoing operation is repeated in reverse, 1. e. T2 again becomes conducting and T1 becomes non-conducting. It will thus be obvious that trigger action is obtained from such an arrangement of two vacuum tubes similar to that of a single gas tube, i. e., a positive impulse applied to the grid of tube T1, for example, causes that tube to conduct which remains conducting after the termination of the impulse.

A counting chain in accordance with the present invention is shown by Fig. 2 in which three trigger circuits A, B and C, each of the character of Fig. 1, are shown connected in such a manner that a change from one stable condition to another will successively occur in each circuit in response to successive positive impulses transmitted over an input circuit IN to the grid of one tube of each trigger. circuit.

In describing the operation of the arrangement of Fig. 2 it will be understood that for proper operation, one tube of each trigger circuit must initially be conducting while its mate is non-conducting and therefore tor the present discussion it will be assumed that the last operation or the chain leit tubes Ta, T: and To conducting and T1, T4 and Te non-conducting.

Assuming as above that T: is initially conducting, plate current will fiow from the positive pole of battery I, low resistance 2, from anode to cathode of tube Ta and through resistance 3 to the grounded negative terminal of the battery. The potentialdifierence across resistance 3. due to this plate current, is applied between the grid and cathode of tube Ts by a connection serially including resistance '4 and the value of resistance 3 will be so chosen that the drop thereacross due to full plate current in tube T: will apply a positive potential to the grid of tube Ts sufiicient to raise it to a valuejust short 01' its critical or "cutoil" point.

A connection including resistance 8 also applies this same potential difference (across resistance 3) between the gridand cathode of tube Ta, which at the time T: fired was non-conducting. This potential difierence, which is insufilcient to raise the grid potential of T to cut-oil, is, in the case of Ta, suificient to raise its grid potential to such a value that the tube will conduct. This dilIerence in the cut-of! potential characteristics between tubes T1, T3 and Ta and tubes T2, T4 and Ts is one of the requirements of the system and is provided for by proper adjustment of the circuit elements.

Raising the grid potential of the tube T2 to cutof! causes that tube to conduct which is efiective to stop T1.

when the first of a succession of positive impulses is applied to the input circuit IN, the grids of tubes T1, '1: and To, which are connected in parallel thereto, are raised in potential and therefore tube Ts, whose grid is just short of cut-oil," as before mentioned due to the potential difference across resistance 3, fires and starts to conduct plate current in a circuit including resistances 5 and l. The potential drop in resistance 1 due to the plate current of tube Ts reduces the potential on the grid or tube Ts thereby rendering this tube non-conducting. Tube Ts now being conducting, the potential difierence across resistance 5 connected in its plate circuit is now effective to raise the grid potential of tube T4 to "cutoil," in a circuit including resistance 9, thus causing that tube to conduct which in turn reduces the potential on the grid of tube T3, thus rendering it non-conducting. The potential diflerence across resistance 5 is also applied to the grid of the next tube in line with T5 (not shown) which primes this tube in readiness to conduct on the next positive pulse, as previously explained in connection with tube Ts.

It will be noted that at the end of the first pulse T: remains in a conducting condition with its mate T1 non-conducting, T4 is conducting, Ts non-conducting. Ta is conducting, To is nonconducting and the tube in line with T5 of the trigger circuit following C (not shown) is primed, i. e., its grid is Just short or cut-oil in readiness to cause that tube to conduct in response to the next impulse.

It will be understood that in case a counting ring is desired of the type described on page 301, et seq. by Wynn-Williams in the paper previously referred to, any number of trigger circuits, conring by coupling the. first and last trigger circuit a,ss4,s79 I v together, i. e., in the case oi Fig. 2 by connecting conductor I I to the grid of tube T1 over conductor l2 and connecting conductor I! to the grid of tube 'I'e over conductor ll.

As is well known the plate current oi any desired tube in the chain can be employed to control any desired counting or recording arrangement.

What is claimed is:-

1. In an impulse counting arrangement comprising a chain of vacuum tube pairs, each tube having an anode, a cathode and a control grid, and so connected and arranged within the respective pairs that a potential applied to the grid of either tube, which raises it abov cut-oil, causes a decrease in current in the anode-cathode circuit of the other tube, characterized by circuit means interconnecting the anode-cathode circuit of the first tube of each pair and the grid of the first tube of the next pair so adjusted that a predetermined current in any one of said anode-cathode circuits will raise the potential of the grid of the succeeding first tube to a potential just short of cut-oil, and other circuit means interconnecting said anode-cathode circuit of each first tube and the'grid oi the companion to the preceding first tube so adjusted that an anode-cathode current in any first tube which increases the grid potential of the succeeding first tube to a point just short of cut-oi! will increase the potential oi the grid of the companion to said preceding first tube to cut-on, and means for simultaneously applying the impulses to be counted to all the first tube grids to raise only the grid near cut-ofi' to that point.

2. In an impulse counting arrangement comprising a chain of vacuum tube pairs, each tube having an anode, a cathode and a control grid and so connected and arranged within the respective pairs that a, potential applied to the grid of either tube which raises it above cut-oi! causes a decrease in current in the anode-cathode circuit of the other tube characterized by circuit means interconnecting the anode-cathode circuit of the first tube of each pair with the grid of the first tube of the succeeding pair and with the grid of the companion to the preceding first tube so adjusted that a, predetermined current in any one of said anode-cathode circuits will raise th grid potential of the succeeding first tube to a point just short of cut-ofi and raise the grid of the companion to the preceding first tube to its cut-off potential, and means for simultaneously applying the impulses to be counted to all the first tube grids to raise the grid which is near cut-ofi, only, to that point.

3. In an impulse counting arrangement comprising a sequential plurality of vacuum tube trigger circuits connected in a closed ring, each trigger circuit employing a pair of thermionic vacuum tubes arranged in such a manner that an increase in plate current in one tube of a pair will drive the potential of the grid of its companion tube below cut-oil. thereby decreasing the plate current therein, means for simultaneously applying the pulses to be counted to the first tube grid of all trigger circuit pairs, means. responsive to a predetermined current flowing in the anodecathode circuit of any first tube to apply a positive potential to the grid of the succeeding first tube to raise its potential just short of the critical potential thereof and to raise the potential of the grid of the companion of the preceding first tube to its critical potential value.

SYDNEY B. INGRAM. 

